Impact of different supply modes of stratum ventilation on airflow and contaminant distribution characteristics

For non-uniform air distribution, the contaminant accumulation occurs in the stagnant zone and leads to high exposure risk. A high supply airflow rate increases the air mixing and contaminant dilution but also the risk of the draft sensation. This study proposes dynamic stratum ventilation with variable supply air direction. The variable supply air direction is achieved by a supply grille with swing flaps. Experiments are conducted with various combinations of the constant/variable supply air direction, high/low supply airflow rate, and different contaminant source locations. The impact of different supply modes of stratum ventilation on the airflow and contaminant distribution characteristics are investigated. For stratum ventilation with the variable supply air direction, the turbulence intensity is quadratic polynomial correlated to the mean air velocity with a coefficient of 0.9853 because the periodically changed supply air direction affects the velocity fluctuation. Stratum ventilation with the variable supply air direction has airflow with the β-value of 1.37–1.59. The different air supply modes influence the horizontal CO₂ distribution differently regarding the location of the contaminant source, which provides new insights into indoor air quality control under stratum ventilation. When the contaminant source is in the mixing zone, stratum ventilation with a high supply airflow rate and variable supply air direction can effectively reduce the draft risk and contaminant concentration. © 2023 Elsevier Ltd.